ZCZC MIATCDEP5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM GEORGETTE DISCUSSION NUMBER 3 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 8 PM PDT THU AUG 26 2004 INFRARED SATELLITE IMAGERY INDICATES A LARGE BURST OF -85C TO -90C CONVECTIVE TOPS HAS PERSISTED OVER AND NEAR THE CENTER OF TROPICAL STORM GEORGETTE OVER THE PAST 5 HOURS AS THE RAGGED BANDING FEATURE NOTED EARLIER IN THE NORTHERN SEMICIRCLE HAS DISSIPATED. THE CENTRAL COLD COVER FEATURE HAS RESULTED IN A SCATTERING OF THE FIX POSITIONS FROM THE THREE SATELLITE AGENCIES...AND THUS LESS CONFIDENCE IN THE INITIAL POSITION AND MOTION. IN ANY EVENT SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM TAFB...35 KT FROM SAB AND AFWA. THE INITIAL INTENSITY OF 40 KT IS ESSENTIALLY A COMPROMISE BETWEEN THE AGENCY ESTIMATES. THE SYSTEM CURRENTLY SHOWS GOOD CIRRUS OUTFLOW OVER ALL QUADRANTS...EXCEPT THE EASTERN QUADRANT WHERE OUTFLOW IS RESTRICTED DUE TO EASTERLY SHEAR. THE INITIAL MOTION IS A RATHER UNCERTAIN 305/14. WATER VAPOR IMAGERY AND LARGE-SCALE MODEL ANALYSES INDICATE THAT GEORGETTE IS SOUTH OF A NARROW MID/UPPER-LEVEL RIDGE AXIS ALONG 29N-30N. THE GLOBAL MODELS FORECAST THE RIDGE TO STRENGTHEN AND BUILD WESTWARD...WHICH SHOULD CAUSE GEORGETTE TO GRADUALLY TURN MORE WESTWARD. NHC TRACK GUIDANCE GENERALLY AGREES WITH THIS SCENARIO...AND AS WAS THE CASE IN THE LAST MODEL CYCLE...THE DYNAMICAL GUIDANCE CALLS FOR A WESTWARD TURN AFTER 36 HR WHILE THE VARIOUS BAM MODELS...LBAR...AND NHC91 MOVE THE CYCLONE WEST-NORTHWESTWARD TO NORTHWESTWARD THROUGH THE FORECAST PERIOD. THE OFFICIAL FORECAST FOLLOWS THE DYNAMICAL GUIDANCE WITH A WESTWARD TURN AFTER 48 HR. THE NEW FORECAST TRACK IS ONLY SLIGHTLY NORTH OF THE PREVIOUS TRACK DUE TO THE INITIAL POSITION AND MOTION. WATER VAPOR IMAGERY INDICATES THAT GEORGETTE IS CURRENTLY EXPERIENCING SOME EASTERLY SHEAR. THE UNIVERSITY OF WISCONSIN CIMSS WIND SHEAR ANALYSIS INDICATES 15-20 KT OF SHEAR OVER GEORGETTE. THE SHEAR IS FORECAST TO WEAKEN OVER THE NEXT 12-24 HOURS AS INDICATED BY THE SHIPS GUIDANCE. STEADY INTENSIFICATION IS FORECAST WITH GEORGETTE ATTAINING HURRICANE STATUS IN 36 HOURS...AND A PEAK INTENSITY OF 70 KT IN 48 HOURS. THIS IS ALONG THE LINES OF BOTH SHIPS AND THE GFDL. BEYOND THAT TIME FRAME...GEORGETTE IS FORECAST TO TRACK OVER COOLER WATERS AND STEADILY WEAKEN. THE GFDL INTENSITY FORECAST WAS PREFERRED OVER THE SHIPS BEYOND 48 HOURS AS THE SHIPS MODEL ONLY WEAKENED GEORGETTE TO 55-60 KT BY DAY 5 DESPITE A TRACK OVER 24-25 DEG C WATERS. FORECASTER COBB/PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 27/0300Z 16.4N 108.8W 40 KT 12HR VT 27/1200Z 17.4N 110.7W 50 KT 24HR VT 28/0000Z 18.2N 113.2W 60 KT 36HR VT 28/1200Z 18.7N 115.7W 65 KT 48HR VT 29/0000Z 19.0N 118.0W 70 KT 72HR VT 30/0000Z 19.5N 122.0W 60 KT 96HR VT 31/0000Z 19.5N 126.5W 45 KT 120HR VT 01/0000Z 19.5N 131.0W 25 KT $$ NNNN
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Page last modified: Friday, 27-Aug-2004 02:33:28 UTC